The purpose of this proposal is to develop a peptide-based technology to capture and expand cancer cells in body fluids, specifically pleural effusion. Pleural effusion is a common complication associated with malignancies especially lung cancer. The sensitivity is generally low in detecting cancer cells in pleural fluid by conventional cytologic methods. Detection of cancer cells in body fluids is commonly limited by the small number of malignant cells which are obscured by the presence of mesothelial cells, normal blood cells, fibroblasts, microorganisms and cellular debris. In our laboratory, we have identified peptide ligands with high affinity for malignant cells using the technology of 'one-bread one-peptide' combinatorial library invented by the co-investigator, Dr. Kit Lam. A sensitive and specific cell-growth-on-bead assay has also been developed in our laboratory for screening millions of peptide beads for specific peptide motifs to use epithelial cancer cells can attach and grow. Using this method, we have identified peptide specific motifs specific for cell- surface receptors of human malignant cell lines such as that from non- small cell lung cancers. To date, we have identified two specific hexapeptides with high affinity for lung cancer cells. Using beads conjugated with these peptides, pilot studies have demonstrated the feasibility of isolating epithelial cells from pleural fluids with proven malignant cells amid a large number of red blood cells and cell debris. We hypothesize that malignant cells from pleural fluid can be isolated, enriched and preserved by the cell-growth-on-bead assay using beads conjugated with the two specific hexapeptide ligands that we have identified to date. The specific aims of this proposal are formulated as cells: 1. To synthesize, in large scale, beads carrying one of these two specific hexapeptide motifs; 2. To optimize conditions of cell-growth- on-bead assay using these peptide beads to capture and expand epithelial cells from pleural fluid; 3. To develop methods to preserve and identify malignant cells enriched from the cell-growth-on-bead assay; 4. To develop a high-yield and high-throughput technology of magnetic peptide-beads for isolating and enriching malignant cells from pleural fluid. The development of this technology will greatly enhance our ability of diagnosing malignant pleural effusion, and it will provide a model for capturing and expanding exfoliated malignant cells in other body fluids.